How can I watch downloaded vidios on my TV ,what do I need to connect them

You just need the right software, which may vary depending upon the format of the videos. Many of the videos that you will find on internet can be played used Windows Media Player (which should be on your machine already is you use Windows), others use Quicktime (which is available here: http://www.apple.com/quicktime/download/). Still others may need other applications. If you find that these applications do not run the videos that you wish to watch, tell us what the extension of the video is and I am sure that either myself or one of the others on this board can help

How can I watch downloaded vidios on my TV ,what do I need to connect from my computer to my television

Here are a few articles you may find helpful:

TakeTV

Movies: From PC to TV - How to Burn, Plug In and Stream Films and TV Shows to Your HDTV - Popular Mechanics

How to use a PC DVD player and watch movies on TV

Vasily

Although these tips are very useful the simplest solution is to purchase (if you don't already have I'm assuming) a S-Video compatible Graphics Card(PCI OR AGP) and the S-Video Cable.

Step 1) After inserting the Video card(64 to 256 MB graphics cards have them), connect the S-Video cable to the back of the video card and the other head at the back of your television. (Hopefully your television has a compatible s-video port)

Step 2) Turn on your television and then your computer. It should automatically detect and display your cpu's content. However if it doesn't and refer to the graphics properties of your video card. (By right clicking on your desktop and going to Display settings) from there you should be able to see a box with multiple displays.

Step 3) If all else fails , install the latest drivers for your graphics card and the Control Panel( if available from your graphics card manufacturer) which will enable you to manually configure the s-video properties(multi display etc).

http://www.teluguone.com/pctotv/images/svido.jpg

Regards,
Jayblaze